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At the ELBE high power radiation facility, the second version of a superconducting radio frequency (SRF) photoinjector has been put into operation and is now routinely applied for user operation at the ELBE electron accelerator. SRF guns are suitable for generating continuous wave (CW) electron beam with high average currents and high beam brightness. The SRF gun at ELBE has the goal to generate short electron pulses with bunch charges of 200-300 pC at typical repetition rates of 100 kHz for the production of super radiant, coherent terahertz radiation. The SRF gun includes a 3.5-cell, 1.3 GHz niobium cavity and a superconducting solenoid. A support system with liquid nitrogen (LN2) cooling allows the operation of normal-conducting, high quantum efficiency photo cathodes. In the paper we present the design and performance of the SRF gun as well as beam measurements for the operation with Mg photocathodes and an acceleration gradient of 8 MV/m (4 MeV kinetic energy). Finally, we discuss the SRF gun application for production of coherent terahertz radiation at the ELBE facility.

In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In our contribution we will report on the commissioning of the SRF gun by presenting a full set of RF performance results as well as detailed beam parameter measurements up to a bunch charge of 300 pC. Additionally, we will present the results of the first two user experiments (neutron and THz generation) that demonstrated the reliability of this gun concept.

In May 2014 the 1st superconducting photo injector (SRF gun) at HZDR was replaced by a new gun, featuring a new resonator and cryostat. The intention for this upgrade was to reach higher beam energy, higher bunch charge and lower emittance at the same time in order to serve user experiments at the superconducting CW accelerator ELBE. In this contribution we will report on the commissioning of the SRF gun by presenting detailed beam parameter measurements up to a bunch charge of 300 pC. Additionally, we will report the results of the first two user experiments (neutron and THz generation) that demonstrated the reliability of this gun concept.

For future linear CW accelerators, superconducting (SC) RF guns are discussed to be the most promising solution to fulfil the demands on high average current and high brightness at the same time. But in difference to the NCRF guns, the application of static magnetic fields near the cathode to compensate for space charge forces is not possible. Instead, magnetic fields of transverse electric (TE) modes excited in parallel to the accelerating mode were proposed. Experiments at the 1st Rossendorf SRF gun using the existing fundamental mode coupler in combination with a RF diplexer have shown that this is feasible. However, since the cavity was not designed for this purpose, the mode was strongly damped by HOM couplers and cavity beam tubes and thus only low field strength could be achieved. In this contribution we will present a modified cavity design that avoids these problems and provides a separate RF coupler for the TE mode. Additionally, we will report on the first vertical test that demonstrated the functionality of the whole RF setup as well as realized significant higher field of the excited TE011 mode in parallel to the TM010 mode.

Superconducting RF injectors are promising candidates for the particle sources of future accelerators. While machines like high power free electron lasers or energy recovery linacs are planned to be operated with large duty factors, or even continuous wave mode, to increase the beam intensity, they also demand high beam quality. As this is already determined at the very start of the generation of each particle bunch, the concept of an SRF gun becomes appealing. Transverse Emittance marks the beam quality which is of tremendous relevance for all beam optics and further more sets the level of angular resolution of any scattering experiment performed with the beam. Several concepts to enhance this quality with the lately comissioned Rossendorf SRF Gun II have been presented in recent year’s conferences. The talk will summarize the expended efforts, discuss some of the reflections on installation and operation of the used tools and present preliminary results of the recent achievements.

Superconducting rf photo electron injectors SRF photoinjectors hold the promise to deliver high brightness, high average current electron beams for future light sources or other applications demanding continuous wave operation of an electron injector. This paper discusses results from beam commissioning of a hybrid SRF photoinjector based on a Pb coated plug and a Nb rf gun cavity for beam energies up to 2.5MeV at Helmholtz Zentrum Berlin HZB . Emittance measurements and transverse phase space characterization with solenoid scan and slitmask methods will be presented

Superconducting RF photo guns are suitable candidates for electron injectors in future free electron lasers and energy recovery linacs. For the radiation source ELBE an SRF gun was build and put into operation. During long term tests, the operation of normal conducting photocathodes in the superconducting cavity has been successfully demonstrated. At moderate average currents of some hundreds of amp; 956;A the Cs2Te photocathodes possess excellent lifetime. The gun s acceleration gradient is the key parameters for beam emittance and the maximum achievable bunch charge of the gun. Therefore two new cavities with higher performance were developed, built and treated. The final tests of these cavities are ongoing. An upgraded cryomodule with an integrated superconducting solenoid was built

Many future electron accelerator projects such as energy recovery linacs (ERLs), high power free electron lasers (FELs) and also some of the new collider designs rely on the development of particle sources which provide them with high average beam currents at high repetition rates, while maintaining a low emittance. Superconducting radio frequency (SRF) photo injectors represent a promising concept to give just that, offering the option of a continuous wave (CW) operation with high bunch charges. Nevertheless, emittance compensation for these electron guns, with the goal of reaching the same level as normal conducting sources, is an ongoing challenge. This paper is going to discuss several approaches for the 3-1/2-cell SRF gun installed at the accelerator facility ELBE at the Helmholtz Center Dresden-Rossendorf including the installation of a superconducting solenoid within the injector’s cryostat and present the currently used method to determine the beam’s phase space.

Superconducting RF photo guns are suitable candidates for electron injectors in future free-electron lasers and energy recovery linacs. For the radiation source ELBE an SRF gun was build and put into operation. During long-term tests, the operation of normal-conducting photocathodes in the superconducting cavity has been successfully demonstrated. At moderate average currents of some hundreds of μA the Cs2Te photocathodes possess excellent lifetime. The gun's acceleration gradient is the key parameters for beam emittance and the maximum achievable bunch charge of the gun. Therefore two new cavities with higher performance were developed, built and treated. The final tests of these cavities are ongoing. An upgraded cryomodule with an integrated superconducting solenoid was built.

A superconducting radio-frequency (SRF) gun with a superconducting Pb photocathode was build up for the first stage of the BERLinPro gun. We report on the activities on the gun and measurements of the beam parameters like beam energy and beam current. Improvement of the quantum efficiency after the laser cleaning treatments is discussed.

Photocathodes are a limiting factor for the next generation of ultra high brightness photoinjector driven accelerators. We studied the behavior of a superconducting Pb cathode in the cryogenic environment of a superconducting rf gun cavity related to the quantum efficiency, its spatial distribution and the work function. Cathode surface contaminations can modify the performance of the photocathodes as well as the gun cavity. We discuss the possibilities to remove these contaminations